From 5c7762841f776d5aec7990985571019a5c518651 Mon Sep 17 00:00:00 2001
From: listerily <listerily@outlook.com>
Date: Fri, 26 May 2023 11:21:30 +0800
Subject: [PATCH] [bug] Fix misbehaviour and assertion error on ti.math.sign

---
 python/taichi/math/mathimpl.py |  2 +-
 tests/python/test_unary_ops.py | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/python/taichi/math/mathimpl.py b/python/taichi/math/mathimpl.py
index 947cea1fb71e9..6bd0b06b01245 100644
--- a/python/taichi/math/mathimpl.py
+++ b/python/taichi/math/mathimpl.py
@@ -273,7 +273,7 @@ def sign(x):
         >>> ti.math.sign(x)
         [-1.000000, 0.000000, 1.000000]
     """
-    return ops.cast((x >= 0.0) - (x <= 0.0), float)
+    return ops.cast((x >= 0.0), float) - ops.cast((x <= 0.0), float)
 
 
 @func
diff --git a/tests/python/test_unary_ops.py b/tests/python/test_unary_ops.py
index 574e5e0d914db..6fe014bee872b 100644
--- a/tests/python/test_unary_ops.py
+++ b/tests/python/test_unary_ops.py
@@ -142,3 +142,14 @@ def test_u32(x: ti.uint32) -> ti.int32:
     assert test_u32(100) == 3
     assert test_u32(1000) == 6
     assert test_u32(10000) == 5
+
+
+@test_utils.test()
+def test_sign():
+    @ti.kernel
+    def foo(val: ti.f32) -> ti.f32:
+        return ti.math.sign(val)
+
+    assert foo(0.5) == 1.0
+    assert foo(-0.5) == -1.0
+    assert foo(0.0) == 0.0